Conventionally, an image forming apparatus includes a sheet feeding device that takes one sheet out of a cassette and conveys the sheet toward an image forming unit. In the sheet feeding device, the sheet taken out of the cassette by a pickup roller is fed in between a conveying roller and a separating roller working as a pair. If sheets are multi-fed in between the conveying roller and the separating roller, the separating roller stops travel of a sheet on a side on which the separating roller is placed, and the conveying roller feeds only one sheet on a side on which the conveying roller is placed toward a downstream in a sheet conveying direction.
A motor as a drive source for the conveying roller may also function to drive a registration roller placed downstream of the sheet conveying direction with respect to the conveying roller. In this case, a device is configured such that, when the motor is driven to rotate in one direction, the conveying roller is thereby driven, and that, when the motor is driven to rotate reversely, the registration roller is thereby driven. Further, in order to cut off transmission of torque (torque acting to convey a sheet in a return direction) from the motor to the conveying roller during the reverse rotation of the motor, a one-way clutch is provided in a mechanism for transmitting torque from the motor to the conveying roller. Only if torque acting in a feed direction in which the conveying roller feeds a sheet toward downstream in the conveying direction is input into the one-way clutch, the one-way clutch allows transmission of the torque from the motor to the conveying roller. If torque acting in the return direction opposite to the feed direction is input into the one-way clutch, the one-way clutch cuts off transmission of the torque from the motor to the conveying roller.
In the aforementioned sheet feeding device, if tightly contacting sheets that are a bundle of sheets from which a staple has been removed, for example, are multi-fed in between the conveying roller and the separating roller, the sheets cannot be separated from each other to become separate sheets between the conveying roller and the separating roller. In this case, a multi-feed detecting sensor provided downstream of the sheet conveying direction with respect to the conveying roller detects multi-feed of the sheets. A user is notified of the multi-feed of the sheets, and convey of the sheets is stopped. Then, the user is required to pull out the sheets held between the conveying roller and the separating roller upstream in the sheet conveying direction by hand and remove the sheets from between the conveying roller and the separating roller.
However, as a result of provision of the one-way clutch in the mechanism for transmitting torque from the motor to the conveying roller, rotation of the conveying roller in the return direction while the motor stops is limited by the one-way clutch. Accordingly, conventionally, a great deal of power is required in pulling out the sheets from between the conveying roller and the separating roller, making removal of sheets by pulling a troublesome task.